One type of transportation system is a generally horizontal transportation system in which passengers are moved in a vehicle or cab in a guideway. A closed loop of cable or rope runs along one side of the guideway, and it has two opposite moving lengths, one that is attached to the vehicle to drive the vehicle back and forth along the length of the guideway. The cable is driven bidirectionally by an electric motor at one end of the guideway, and is controlled by supervisory equipment to control the stopping, starting, acceleration and speed of the car. The cable rides on sheaves that are located along the side of the guideway. An arm that extends from the vehicle connects to the cable which drives the vehicle. The guideway determines the general direction of the vehicle, and the cable provides the driving force for moving it in the guideway, but directional control is provided to the vehicle by a guiderail that extends along the length of the guideway in conjunction with a rail follower on the vehicle. The arm and the rail follower comprise a "bogie."
In straight sections of the guideway the sheaves that support both lengths of the cable are primarily vertical to support the weight of the cable. But, in curved sections of the guideway, where the vehicle turns left or right, the particular sheave that supports that length of cable that drives the vehicle is oriented slightly horizontal to accommodate the combined horizontal and vertical loads created in turns.